1. Field
The disclosure relates to a method, system, and article of manufacture for storing redundant segments and parity information for segmented logical volumes.
2. Background
In certain virtual tape storage systems, hard disk drive storage may be used to emulate tape drives and tape cartridges. For instance, host systems may perform input/output (I/O) operations with respect to a tape library by performing I/O operations with respect to a set of hard disk drives that emulate the tape library. In certain virtual tape storage systems at least one virtual tape server (VTS) is coupled to a tape library comprising numerous tape drives and tape cartridges. The VTS is also coupled to a direct access storage device (DASD), comprised of numerous interconnected hard disk drives.
The DASD functions as a cache to volumes in the tape library. In VTS operations, the VTS processes the host's requests to access a volume in the tape library and returns data for such requests, if possible, from the cache. If the volume is not in the cache, then the VTS recalls the volume from the tape library to the cache, i.e., the VTS transfers data from the tape library to the cache. The VTS can respond to host requests for volumes that are present in the cache substantially faster than requests for volumes that have to be recalled from the tape library to the cache. However, since the capacity of the cache is relatively small when compared to the capacity of the tape library, not all volumes can be kept in the cache. Hence, the VTS may migrate volumes from the cache to the tape library, i.e., the VTS may transfer data from the cache to the tape cartridges in the tape library.